Reinforced concrete structures are currently under the threat of both fire and blast. The absence of theoretical methods demonstrates a drawback in the assessment of blast-resistant structures after exposure to fire. A modified layered-section method was developed in this article, which was not only able to determine the complete static resistance-deflection curves of fire-damaged reinforced concrete beams but also able to predict the responses of reinforced concrete beams subjected to blast after fire exposure. The hightemperature effects and the strain-rate effects were included in the concrete and steel material models in the proposed method. A corresponding calculation program FBBA was also compiled based on the explicit Newmark algorithm on the platform of Maple software. The developed method and program were validated by the existing test results. Analytical results showed that after fire exposure, the reinforced concrete beams show significant degradation in the residual bearing capacity, but increase in the ductility. The higher the steel reinforcement ratio, the more degradation the bearing capacity of reinforced concrete beams after fire exposure suffers. The blast resistance of the fired reinforced concrete beams was underestimated without considering the strain-rate effects or just considering the average strain-rate effects.

The bending behavior of reinforced concrete beams under uniform pressure is critical for the research of the blast-resistance performance of structural components under explosive loads. In this study, a bending test of five reinforced concrete beams with the dimensions of 200 mm (width) × 200 mm (depth) × 2500 mm (length) under uniform load produced by a specific cylinder-shaped rubber bag filled with air or water was conducted to investigate their flexural performances. An air bag load was applied to three of the reinforced concrete beams, a water bag load was applied to one reinforced concrete beam, and the remainder beam was subjected to the 4-point bending load. The experimental results highlighted that the air bag and water bag loading methods can be used to effectively apply uniform loads to reinforced concrete beams. Moreover, the stiffness of the air bag was improved by 123% in accordance with the initial pressure increases from 0.15 to 0.45 MPa. In addition, a finite element model of the test loading system was established using ABAQUS/Standard software. Moreover, the critical factors of the air bag loading method were analyzed using the numerical model. The calculated results were found to be in good agreement with the test data. The established finite element model can therefore be used to accurately simulate the action performances of the uniform loading technique using rubber bags filled with air or water.

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